According to a conventional electromagnetic relay, as illustrated in FIG. 21, a terminal case 103 is mounted on a box-shaped main case 102 accommodating an electromagnet unit 101 therein, and a free end portion 106a of an armature 106 which is actuated by the electromagnet unit 101 is engaged with a moveable insulated member 105 for opening and closing contacts in a contact unit 104 incorporated in the terminal case 103 in such a manner that fixed contacts 109 of screw terminal pieces 108 for fixed contacts (FIG. 22) interposed between barriers 107 provided in the terminal case 103 may be opened and closed by moveable contacts 110 carried by the moveable insulated member 105.
According to a conventional structure for mounting the screw terminal pieces 108 between the barriers 107, the screw terminal pieces 108 are inserted from a lower end of the terminal case 103, and are pushed further therefrom towards their free ends until the free ends are placed upon a shelf portion 111 formed in the terminal case 102 as illustrated in FIG. 22.
In this case, the electromagnet unit 101 is inserted into the main case 102 from above and the terminal case 103 is also mounted on the main case 102 from above while the screw terminal pieces 108 are required to be inserted into the terminal case 103 from below, with the result that a considerable amount of effort is required for assembly work, and the screw terminal pieces 108 are not well stabilized as they simply sit on the shelf portion 111. In particular, because the screw terminal pieces 108 are required to be inserted from below, the terminal case 103 must have an open bottom, and it creates the risk of breaking insulation between the contact unit 104 and the electromagnet unit 101 due to the difference in their voltage levels. Therefore, an insulating plate 112 is required to be placed between the terminal case 103 and the main case 102, and this increases the number of component parts and the effort required to assemble it.